The present invention relates to a radio apparatus and particularly, but not exclusively, to a physical small apparatus having a loop antenna, for example a pager. The present invention also relates to a loop antenna.
The use of loop antennas in pagers is known and typically the antenna is a strip of metal bent to a desired shape and a single variable capacitor is connected across the ends of the loop for tuning the antenna. Since pagers are intended to be low cost products, component costs are minimised wherever appropriate and low cost variable capacitors have the drawbacks of being generally lossy at the frequencies of interest and can have a poor temperature performance. Further the use of a single variable capacitor for tuning the antenna over a wide frequency range has the disadvantage that the tuning is critical.